Recomendamos encarecidamente consultar la siguiente publicación como requisito previo para esta publicación.
Lista enlazada Introducción
Insertar un Node en una lista enlazada individualmente
Una lista enlazada doblemente ( DLL ) contiene un puntero adicional, normalmente llamado puntero anterior , junto con el puntero siguiente y los datos que están allí en la lista enlazada individualmente.
A continuación se muestra la representación de un Node DLL en lenguaje C.
C++
/* Node of a doubly linked list */
class Node
{
public:
int data;
Node* next; // Pointer to next node in DLL
Node* prev; // Pointer to previous node in DLL
};
// This code is contributed by shivanisinghss2110
C
/* Node of a doubly linked list */
struct Node {
int data;
struct Node* next; // Pointer to next node in DLL
struct Node* prev; // Pointer to previous node in DLL
};
Java
// Class for Doubly Linked List
public class DLL {
Node head; // head of list
/* Doubly Linked list Node*/
class Node {
int data;
Node prev;
Node next;
// Constructor to create a new node
// next and prev is by default initialized as null
Node(int d) { data = d; }
}
}
Python3
# Node of a doubly linked list class Node: def __init__(self, next=None, prev=None, data=None): self.next = next # reference to next node in DLL self.prev = prev # reference to previous node in DLL self.data = data
C#
// Class for Doubly Linked List
public class DLL {
Node head; // head of list
/* Doubly Linked list Node*/
public class Node {
public int data;
public Node prev;
public Node next;
// Constructor to create a new node
// next and prev is by default initialized as null
Node(int d) { data = d; }
}
}
// This code contributed by gauravrajput1
Javascript
<script>
// Class for Doubly Linked List
var head; // head of list
/* Doubly Linked list Node */
class Node {
// Constructor to create a new node
// next and prev is by default initialized as null
constructor(val) {
this.data = val;
this.prev = null;
this.next = null;
}
}
// This code contributed by gauravrajput1
</script>
Las siguientes son las ventajas/desventajas de la lista de enlaces dobles sobre la lista de enlaces simples.
Ventajas sobre la lista enlazada individualmente
1) Una DLL se puede recorrer tanto hacia adelante como hacia atrás.
2) La operación de eliminación en DLL es más eficiente si se proporciona un puntero al Node que se eliminará.
3) Podemos insertar rápidamente un nuevo Node antes de un Node dado.
En una lista enlazada individualmente, para eliminar un Node, se necesita un puntero al Node anterior. Para obtener este Node anterior, a veces se recorre la lista. En DLL, podemos obtener el Node anterior usando el puntero anterior.
Desventajas sobre la lista enlazada individualmente
1) Cada Node de DLL Requiere espacio adicional para un puntero anterior. Sin embargo, es posible implementar DLL con un solo puntero (consulte this y this ).
2) Todas las operaciones requieren un puntero extra previo para ser mantenidas. Por ejemplo, en la inserción, necesitamos modificar los punteros anteriores junto con los punteros siguientes. Por ejemplo, en las siguientes funciones para inserciones en diferentes posiciones, necesitamos 1 o 2 pasos adicionales para establecer el puntero anterior.
Inserción
Un Node se puede agregar de cuatro maneras
1) Al frente de la DLL
2) Después de un Node dado.
3) Al final de la DLL
4) Antes de un Node dado.
1) Agregar un Node al frente: (un proceso de 5 pasos)
El nuevo Node siempre se agrega antes del encabezado de la lista enlazada dada. Y el Node recién agregado se convierte en el nuevo jefe de DLL. Por ejemplo, si la lista enlazada dada es 10152025 y agregamos un elemento 5 al frente, entonces la lista enlazada se convierte en 510152025. Llamemos a la función que agrega al frente de la lista push(). Push() debe recibir un puntero al puntero principal, porque push debe cambiar el puntero principal para apuntar al nuevo Node (Ver esto )
Los siguientes son los 5 pasos para agregar un Node en la parte delantera.
C++
/* Given a reference (pointer to pointer)
to the head of a list
and an int, inserts a new node on the
front of the list. */
void push(Node** head_ref, int new_data)
{
/* 1. allocate node */
Node* new_node = new Node();
/* 2. put in the data */
new_node->data = new_data;
/* 3. Make next of new node as head
and previous as NULL */
new_node->next = (*head_ref);
new_node->prev = NULL;
/* 4. change prev of head node to new node */
if ((*head_ref) != NULL)
(*head_ref)->prev = new_node;
/* 5. move the head to point to the new node */
(*head_ref) = new_node;
}
// This code is contributed by shivanisinghss2110
C
/* Given a reference (pointer to pointer) to the head of a list
and an int, inserts a new node on the front of the list. */
void push(struct Node** head_ref, int new_data)
{
/* 1. allocate node */
struct Node* new_node = (struct Node*)malloc(sizeof(struct Node));
/* 2. put in the data */
new_node->data = new_data;
/* 3. Make next of new node as head and previous as NULL */
new_node->next = (*head_ref);
new_node->prev = NULL;
/* 4. change prev of head node to new node */
if ((*head_ref) != NULL)
(*head_ref)->prev = new_node;
/* 5. move the head to point to the new node */
(*head_ref) = new_node;
}
Java
// Adding a node at the front of the list
public void push(int new_data)
{
/* 1. allocate node
* 2. put in the data */
Node new_Node = new Node(new_data);
/* 3. Make next of new node as head and previous as NULL */
new_Node.next = head;
new_Node.prev = null;
/* 4. change prev of head node to new node */
if (head != null)
head.prev = new_Node;
/* 5. move the head to point to the new node */
head = new_Node;
}
Python3
# Adding a node at the front of the list def push(self, new_data): # 1 & 2: Allocate the Node & Put in the data new_node = Node(data = new_data) # 3. Make next of new node as head and previous as NULL new_node.next = self.head new_node.prev = None # 4. change prev of head node to new node if self.head is not None: self.head.prev = new_node # 5. move the head to point to the new node self.head = new_node # This code is contributed by jatinreaper
C#
// Adding a node at the front of the list
public void push(int new_data)
{
/* 1. allocate node
* 2. put in the data */
Node new_Node = new Node(new_data);
/* 3. Make next of new node as head and previous as NULL */
new_Node.next = head;
new_Node.prev = null;
/* 4. change prev of head node to new node */
if (head != null)
head.prev = new_Node;
/* 5. move the head to point to the new node */
head = new_Node;
}
// This code is contributed by aashish1995
Javascript
// Adding a node at the front of the list
function push(new_data)
{
/* 1. allocate node
* 2. put in the data */
let new_Node = new Node(new_data);
/* 3. Make next of new node as head and previous as NULL */
new_Node.next = head;
new_Node.prev = null;
/* 4. change prev of head node to new node */
if (head != null)
head.prev = new_Node;
/* 5. move the head to point to the new node */
head = new_Node;
}
// This code is contributed by saurabh_jaiswal.
Cuatro pasos de los cinco pasos anteriores son los mismos que los 4 pasos utilizados para insertar en la parte delantera de una lista enlazada individualmente . El único paso adicional es cambiar el anterior de la cabeza.
2) Agregar un Node después de un Node dado.: (Un proceso de 7 pasos)
Se nos da un puntero a un Node como prev_node, y el nuevo Node se inserta después del Node dado.
C++
/* Given a node as prev_node, insert
a new node after the given node */
void insertAfter(Node* prev_node, int new_data)
{
/*1. check if the given prev_node is NULL */
if (prev_node == NULL)
{
cout<<"the given previous node cannot be NULL";
return;
}
/* 2. allocate new node */
Node* new_node = new Node();
/* 3. put in the data */
new_node->data = new_data;
/* 4. Make next of new node as next of prev_node */
new_node->next = prev_node->next;
/* 5. Make the next of prev_node as new_node */
prev_node->next = new_node;
/* 6. Make prev_node as previous of new_node */
new_node->prev = prev_node;
/* 7. Change previous of new_node's next node */
if (new_node->next != NULL)
new_node->next->prev = new_node;
}
// This code is contributed by shivanisinghss2110.
C
/* Given a node as prev_node, insert a new node after the given node */
void insertAfter(struct Node* prev_node, int new_data)
{
/*1. check if the given prev_node is NULL */
if (prev_node == NULL) {
printf("the given previous node cannot be NULL");
return;
}
/* 2. allocate new node */
struct Node* new_node = (struct Node*)malloc(sizeof(struct Node));
/* 3. put in the data */
new_node->data = new_data;
/* 4. Make next of new node as next of prev_node */
new_node->next = prev_node->next;
/* 5. Make the next of prev_node as new_node */
prev_node->next = new_node;
/* 6. Make prev_node as previous of new_node */
new_node->prev = prev_node;
/* 7. Change previous of new_node's next node */
if (new_node->next != NULL)
new_node->next->prev = new_node;
}
Java
/* Given a node as prev_node, insert a new node after the given node */
public void InsertAfter(Node prev_Node, int new_data)
{
/*1. check if the given prev_node is NULL */
if (prev_Node == null) {
System.out.println("The given previous node cannot be NULL ");
return;
}
/* 2. allocate node
* 3. put in the data */
Node new_node = new Node(new_data);
/* 4. Make next of new node as next of prev_node */
new_node.next = prev_Node.next;
/* 5. Make the next of prev_node as new_node */
prev_Node.next = new_node;
/* 6. Make prev_node as previous of new_node */
new_node.prev = prev_Node;
/* 7. Change previous of new_node's next node */
if (new_node.next != null)
new_node.next.prev = new_node;
}
Python3
# Given a node as prev_node, insert
# a new node after the given node
def insertAfter(self, prev_node, new_data):
# 1. check if the given prev_node is NULL
if prev_node is None:
print("This node doesn't exist in DLL")
return
#2. allocate node & 3. put in the data
new_node = Node(data = new_data)
# 4. Make next of new node as next of prev_node
new_node.next = prev_node.next
# 5. Make the next of prev_node as new_node
prev_node.next = new_node
# 6. Make prev_node as previous of new_node
new_node.prev = prev_node
# 7. Change previous of new_node's next node */
if new_node.next is not None:
new_node.next.prev = new_node
# This code is contributed by jatinreaper
C#
/* Given a node as prev_node, insert a new node after the given node */
public void InsertAfter(Node prev_Node, int new_data)
{
/*1. check if the given prev_node is NULL */
if (prev_Node == null) {
Console.WriteLine("The given previous node cannot be NULL ");
return;
}
/* 2. allocate node
* 3. put in the data */
Node new_node = new Node(new_data);
/* 4. Make next of new node as next of prev_node */
new_node.next = prev_Node.next;
/* 5. Make the next of prev_node as new_node */
prev_Node.next = new_node;
/* 6. Make prev_node as previous of new_node */
new_node.prev = prev_Node;
/* 7. Change previous of new_node's next node */
if (new_node.next != null)
new_node.next.prev = new_node;
}
// This code is contributed by aashish1995
Javascript
<script>
function InsertAfter(prev_Node,new_data)
{
/*1. check if the given prev_node is NULL */
if (prev_Node == null) {
document.write("The given previous node cannot be NULL <br>");
return;
}
/* 2. allocate node
* 3. put in the data */
let new_node = new Node(new_data);
/* 4. Make next of new node as next of prev_node */
new_node.next = prev_Node.next;
/* 5. Make the next of prev_node as new_node */
prev_Node.next = new_node;
/* 6. Make prev_node as previous of new_node */
new_node.prev = prev_Node;
/* 7. Change previous of new_node's next node */
if (new_node.next != null)
new_node.next.prev = new_node;
}
// This code is contributed by unknown2108
</script>
Cinco de los pasos anteriores son los mismos que los 5 pasos utilizados para insertar después de un Node determinado en una lista de enlaces simples . Los dos pasos adicionales son necesarios para cambiar el puntero anterior del nuevo Node y el puntero anterior del siguiente Node del nuevo Node.
3) Agregar un Node al final: (proceso de 7 pasos)
El nuevo Node siempre se agrega después del último Node de la lista enlazada dada. Por ejemplo, si la DLL dada es 510152025 y agregamos un elemento 30 al final, entonces la DLL se convierte en 51015202530.
Dado que una Lista Vinculada generalmente se representa por el encabezado de la misma, tenemos que recorrer la lista hasta el final y luego cambiar la siguiente del último Node al nuevo Node.
Los siguientes son los 7 pasos para agregar un Node al final.
C++
/* Given a reference (pointer to pointer) to the head
of a DLL and an int, appends a new node at the end */
void append(Node** head_ref, int new_data)
{
/* 1. allocate node */
Node* new_node = new Node();
Node* last = *head_ref; /* used in step 5*/
/* 2. put in the data */
new_node->data = new_data;
/* 3. This new node is going to be the last node, so
make next of it as NULL*/
new_node->next = NULL;
/* 4. If the Linked List is empty, then make the new
node as head */
if (*head_ref == NULL)
{
new_node->prev = NULL;
*head_ref = new_node;
return;
}
/* 5. Else traverse till the last node */
while (last->next != NULL)
last = last->next;
/* 6. Change the next of last node */
last->next = new_node;
/* 7. Make last node as previous of new node */
new_node->prev = last;
return;
}
// This code is contributed by shivanisinghss2110
C
/* Given a reference (pointer to pointer) to the head
of a DLL and an int, appends a new node at the end */
void append(struct Node** head_ref, int new_data)
{
/* 1. allocate node */
struct Node* new_node = (struct Node*)malloc(sizeof(struct Node));
struct Node* last = *head_ref; /* used in step 5*/
/* 2. put in the data */
new_node->data = new_data;
/* 3. This new node is going to be the last node, so
make next of it as NULL*/
new_node->next = NULL;
/* 4. If the Linked List is empty, then make the new
node as head */
if (*head_ref == NULL) {
new_node->prev = NULL;
*head_ref = new_node;
return;
}
/* 5. Else traverse till the last node */
while (last->next != NULL)
last = last->next;
/* 6. Change the next of last node */
last->next = new_node;
/* 7. Make last node as previous of new node */
new_node->prev = last;
return;
}
Java
// Add a node at the end of the list
void append(int new_data)
{
/* 1. allocate node
* 2. put in the data */
Node new_node = new Node(new_data);
Node last = head; /* used in step 5*/
/* 3. This new node is going to be the last node, so
* make next of it as NULL*/
new_node.next = null;
/* 4. If the Linked List is empty, then make the new
* node as head */
if (head == null) {
new_node.prev = null;
head = new_node;
return;
}
/* 5. Else traverse till the last node */
while (last.next != null)
last = last.next;
/* 6. Change the next of last node */
last.next = new_node;
/* 7. Make last node as previous of new node */
new_node.prev = last;
}
Python3
# Add a node at the end of the DLL def append(self, new_data): # 1. allocate node 2. put in the data new_node = Node(data = new_data) last = self.head # 3. This new node is going to be the # last node, so make next of it as NULL new_node.next = None # 4. If the Linked List is empty, then # make the new node as head if self.head is None: new_node.prev = None self.head = new_node return # 5. Else traverse till the last node while (last.next is not None): last = last.next # 6. Change the next of last node last.next = new_node # 7. Make last node as previous of new node */ new_node.prev = last # This code is contributed by jatinreaper
C#
// Add a node at the end of the list
void append(int new_data)
{
/* 1. allocate node
* 2. put in the data */
Node new_node = new Node(new_data);
Node last = head; /* used in step 5*/
/* 3. This new node is going
to be the last node, so
* make next of it as NULL*/
new_node.next = null;
/* 4. If the Linked List is empty,
then make the new * node as head */
if (head == null)
{
new_node.prev = null;
head = new_node;
return;
}
/* 5. Else traverse till the last node */
while (last.next != null)
last = last.next;
/* 6. Change the next of last node */
last.next = new_node;
/* 7. Make last node as previous of new node */
new_node.prev = last;
}
// This code is contributed by shivanisinghss2110
Javascript
<script>
// Add a node at the end of the list
function append(new_data)
{
/* 1. allocate node
* 2. put in the data */
var new_node = new Node(new_data);
var last = head; /* used in step 5*/
/* 3. This new node is going to be the last node, so
* make next of it as NULL*/
new_node.next = null;
/* 4. If the Linked List is empty, then make the new
* node as head */
if (head == null) {
new_node.prev = null;
head = new_node;
return;
}
/* 5. Else traverse till the last node */
while (last.next != null)
last = last.next;
/* 6. Change the next of last node */
last.next = new_node;
/* 7. Make last node as previous of new node */
new_node.prev = last;
}
// This code is contributed by Rajput-Ji
</script>
Seis de los 7 pasos anteriores son los mismos que los 6 pasos utilizados para insertar después de un Node dado en una lista de enlaces simples . Se necesita un paso adicional para cambiar el puntero anterior del nuevo Node.
4) Agregue un Node antes de un Node dado:
Pasos
Deje que el puntero a este Node dado sea next_node y que los datos del nuevo Node se agreguen como new_data.
- Compruebe si next_node es NULL o no. Si es NULL, regrese de la función porque no se puede agregar ningún Node nuevo antes de NULL
- Asigne memoria para el nuevo Node, que se llame new_node
- Establecer nuevo_Node->datos = nuevos_datos
- Establezca el puntero anterior de este new_node como el Node anterior del next_node, new_node->prev = next_node->prev
- Establezca el puntero anterior de next_node como new_node, next_node->prev = new_node
- Establezca el siguiente puntero de este new_node como next_node, new_node->next = next_node;
- Si el Node anterior de new_node no es NULL, establezca el siguiente puntero de este Node anterior como new_node, new_node->prev->next = new_node
- De lo contrario, si la anterior de new_node es NULL, será el nuevo Node principal. Entonces, haz (*head_ref) = new_node.
A continuación se muestra la implementación del enfoque anterior:
Bloque de código
Producción:
La DLL creada es:
Transversal en dirección hacia adelante
9 1 5 7 6
Recorrido en sentido inverso
6 7 5 1 9
Un programa de trabajo completo para probar las funciones anteriores.
El siguiente es un programa completo para probar las funciones anteriores.
C++
// A complete working C++ program to
// demonstrate all insertion methods
#include <bits/stdc++.h>
using namespace std;
// A linked list node
class Node
{
public:
int data;
Node* next;
Node* prev;
};
/* Given a reference (pointer to pointer)
to the head of a list
and an int, inserts a new node on the
front of the list. */
void push(Node** head_ref, int new_data)
{
/* 1. allocate node */
Node* new_node = new Node();
/* 2. put in the data */
new_node->data = new_data;
/* 3. Make next of new node as head
and previous as NULL */
new_node->next = (*head_ref);
new_node->prev = NULL;
/* 4. change prev of head node to new node */
if ((*head_ref) != NULL)
(*head_ref)->prev = new_node;
/* 5. move the head to point to the new node */
(*head_ref) = new_node;
}
/* Given a node as prev_node, insert
a new node after the given node */
void insertAfter(Node* prev_node, int new_data)
{
/*1. check if the given prev_node is NULL */
if (prev_node == NULL)
{
cout<<"the given previous node cannot be NULL";
return;
}
/* 2. allocate new node */
Node* new_node = new Node();
/* 3. put in the data */
new_node->data = new_data;
/* 4. Make next of new node as next of prev_node */
new_node->next = prev_node->next;
/* 5. Make the next of prev_node as new_node */
prev_node->next = new_node;
/* 6. Make prev_node as previous of new_node */
new_node->prev = prev_node;
/* 7. Change previous of new_node's next node */
if (new_node->next != NULL)
new_node->next->prev = new_node;
}
/* Given a reference (pointer to pointer) to the head
of a DLL and an int, appends a new node at the end */
void append(Node** head_ref, int new_data)
{
/* 1. allocate node */
Node* new_node = new Node();
Node* last = *head_ref; /* used in step 5*/
/* 2. put in the data */
new_node->data = new_data;
/* 3. This new node is going to be the last node, so
make next of it as NULL*/
new_node->next = NULL;
/* 4. If the Linked List is empty, then make the new
node as head */
if (*head_ref == NULL)
{
new_node->prev = NULL;
*head_ref = new_node;
return;
}
/* 5. Else traverse till the last node */
while (last->next != NULL)
last = last->next;
/* 6. Change the next of last node */
last->next = new_node;
/* 7. Make last node as previous of new node */
new_node->prev = last;
return;
}
// This function prints contents of
// linked list starting from the given node
void printList(Node* node)
{
Node* last;
cout<<"\nTraversal in forward direction \n";
while (node != NULL)
{
cout<<" "<<node->data<<" ";
last = node;
node = node->next;
}
cout<<"\nTraversal in reverse direction \n";
while (last != NULL)
{
cout<<" "<<last->data<<" ";
last = last->prev;
}
}
/* Driver program to test above functions*/
int main()
{
/* Start with the empty list */
Node* head = NULL;
// Insert 6. So linked list becomes 6->NULL
append(&head, 6);
// Insert 7 at the beginning. So
// linked list becomes 7->6->NULL
push(&head, 7);
// Insert 1 at the beginning. So
// linked list becomes 1->7->6->NULL
push(&head, 1);
// Insert 4 at the end. So linked
// list becomes 1->7->6->4->NULL
append(&head, 4);
// Insert 8, after 7. So linked
// list becomes 1->7->8->6->4->NULL
insertAfter(head->next, 8);
cout << "Created DLL is: ";
printList(head);
return 0;
}
// This is code is contributed by rathbhupendra
C
// A complete working C program to
// demonstrate all insertion
// methods
#include <stdio.h>
#include <stdlib.h>
// A linked list node
struct Node {
int data;
struct Node* next;
struct Node* prev;
};
/* Given a reference (pointer to pointer) to the head of a
list and an int, inserts a new node on the front of the
list. */
void push(struct Node** head_ref, int new_data)
{
/* 1. allocate node */
struct Node* new_node
= (struct Node*)malloc(sizeof(struct Node));
/* 2. put in the data */
new_node->data = new_data;
/* 3. Make next of new node as head and previous as NULL
*/
new_node->next = (*head_ref);
new_node->prev = NULL;
/* 4. change prev of head node to new node */
if ((*head_ref) != NULL)
(*head_ref)->prev = new_node;
/* 5. move the head to point to the new node */
(*head_ref) = new_node;
}
/* Given a node as prev_node, insert a new node after the
* given node */
void insertAfter(struct Node* prev_node, int new_data)
{
/*1. check if the given prev_node is NULL */
if (prev_node == NULL) {
printf("the given previous node cannot be NULL");
return;
}
/* 2. allocate new node */
struct Node* new_node
= (struct Node*)malloc(sizeof(struct Node));
/* 3. put in the data */
new_node->data = new_data;
/* 4. Make next of new node as next of prev_node */
new_node->next = prev_node->next;
/* 5. Make the next of prev_node as new_node */
prev_node->next = new_node;
/* 6. Make prev_node as previous of new_node */
new_node->prev = prev_node;
/* 7. Change previous of new_node's next node */
if (new_node->next != NULL)
new_node->next->prev = new_node;
}
/* Given a reference (pointer to pointer) to the head
of a DLL and an int, appends a new node at the end */
void append(struct Node** head_ref, int new_data)
{
/* 1. allocate node */
struct Node* new_node
= (struct Node*)malloc(sizeof(struct Node));
struct Node* last = *head_ref; /* used in step 5*/
/* 2. put in the data */
new_node->data = new_data;
/* 3. This new node is going to be the last node, so
make next of it as NULL*/
new_node->next = NULL;
/* 4. If the Linked List is empty, then make the new
node as head */
if (*head_ref == NULL) {
new_node->prev = NULL;
*head_ref = new_node;
return;
}
/* 5. Else traverse till the last node */
while (last->next != NULL)
last = last->next;
/* 6. Change the next of last node */
last->next = new_node;
/* 7. Make last node as previous of new node */
new_node->prev = last;
return;
}
// This function prints contents of linked list starting
// from the given node
void printList(struct Node* node)
{
struct Node* last;
printf("\nTraversal in forward direction \n");
while (node != NULL) {
printf(" %d ", node->data);
last = node;
node = node->next;
}
printf("\nTraversal in reverse direction \n");
while (last != NULL) {
printf(" %d ", last->data);
last = last->prev;
}
}
/* Driver program to test above functions*/
int main()
{
/* Start with the empty list */
struct Node* head = NULL;
// Insert 6. So linked list becomes 6->NULL
append(&head, 6);
// Insert 7 at the beginning. So linked list becomes
// 7->6->NULL
push(&head, 7);
// Insert 1 at the beginning. So linked list becomes
// 1->7->6->NULL
push(&head, 1);
// Insert 4 at the end. So linked list becomes
// 1->7->6->4->NULL
append(&head, 4);
// Insert 8, after 7. So linked list becomes
// 1->7->8->6->4->NULL
insertAfter(head->next, 8);
printf("Created DLL is: ");
printList(head);
getchar();
return 0;
}
Java
// A complete working Java program to demonstrate all
// Class for Doubly Linked List
public class DLL {
Node head; // head of list
/* Doubly Linked list Node*/
class Node {
int data;
Node prev;
Node next;
// Constructor to create a new node
// next and prev is by default initialized as null
Node(int d) { data = d; }
}
// Adding a node at the front of the list
public void push(int new_data)
{
/* 1. allocate node
* 2. put in the data */
Node new_Node = new Node(new_data);
/* 3. Make next of new node as head and previous as NULL */
new_Node.next = head;
new_Node.prev = null;
/* 4. change prev of head node to new node */
if (head != null)
head.prev = new_Node;
/* 5. move the head to point to the new node */
head = new_Node;
}
// Add a node before the given node
public void InsertBefore(Node next_node, int new_data)
{
/*Check if the given nx_node is NULL*/
if(next_node == null)
{
System.out.println("The given next node can not be NULL");
return;
}
//Allocate node, put in the data
Node new_node = new Node(new_data);
//Making prev of new node as prev of next node
new_node.prev = next_node.prev;
//Making prev of next node as new node
next_node.prev = new_node;
//Making next of new node as next node
new_node.next = next_node;
//Check if new node is added as head
if(new_node.prev != null)
new_node.prev.next = new_node;
else
head = new_node;
}
/* Given a node as prev_node, insert
a new node after the given node */
public void InsertAfter(Node prev_Node, int new_data)
{
/*1. check if the given prev_node is NULL */
if (prev_Node == null) {
System.out.println("The given previous node cannot be NULL ");
return;
}
/* 2. allocate node
* 3. put in the data */
Node new_node = new Node(new_data);
/* 4. Make next of new node as next of prev_node */
new_node.next = prev_Node.next;
/* 5. Make the next of prev_node as new_node */
prev_Node.next = new_node;
/* 6. Make prev_node as previous of new_node */
new_node.prev = prev_Node;
/* 7. Change previous of new_node's next node */
if (new_node.next != null)
new_node.next.prev = new_node;
/*8. Maintaining tail node if we are inserting after the second last node */
if (newNode.next==null){
tail = newNode;
}
}
// Add a node at the end of the list
void append(int new_data)
{
/* 1. allocate node
* 2. put in the data */
Node new_node = new Node(new_data);
Node last = head; /* used in step 5*/
/* 3. This new node is going to be the last node, so
* make next of it as NULL*/
new_node.next = null;
/* 4. If the Linked List is empty, then make the new
* node as head */
if (head == null) {
new_node.prev = null;
head = new_node;
return;
}
/* 5. Else traverse till the last node */
while (last.next != null)
last = last.next;
/* 6. Change the next of last node */
last.next = new_node;
/* 7. Make last node as previous of new node */
new_node.prev = last;
}
// This function prints contents of
// linked list starting from the given node
public void printlist(Node node)
{
Node last = null;
System.out.println("Traversal in forward Direction");
while (node != null) {
System.out.print(node.data + " ");
last = node;
node = node.next;
}
System.out.println();
System.out.println("Traversal in reverse direction");
while (last != null) {
System.out.print(last.data + " ");
last = last.prev;
}
}
/* Driver program to test above functions*/
public static void main(String[] args)
{
/* Start with the empty list */
DLL dll = new DLL();
// Insert 6. So linked list becomes 6->NULL
dll.append(6);
// Insert 7 at the beginning. So
// linked list becomes 7->6->NULL
dll.push(7);
// Insert 1 at the beginning. So
// linked list becomes 1->7->6->NULL
dll.push(1);
// Insert 4 at the end. So linked
// list becomes 1->7->6->4->NULL
dll.append(4);
// Insert 8, after 7. So linked
// list becomes 1->7->8->6->4->NULL
dll.InsertAfter(dll.head.next, 8);
// Insert 5, before 8.So linked
// list becomes 1->7->5->8->6->4
dll.InsertBefore(dll.head.next.next, 5);
System.out.println("Created DLL is: ");
dll.printlist(dll.head);
}
}
// This code is contributed by Sumit Ghosh
Python3
# A complete working Python
# program to demonstrate all
# insertion methods
# A linked list node
class Node:
# Constructor to create a new node
def __init__(self, data):
self.data = data
self.next = None
self.prev = None
# Class to create a Doubly Linked List
class DoublyLinkedList:
# Constructor for empty Doubly Linked List
def __init__(self):
self.head = None
# Given a reference to the head of a list and an
# integer, inserts a new node on the front of list
def push(self, new_data):
# 1. Allocates node
# 2. Put the data in it
new_node = Node(new_data)
# 3. Make next of new node as head and
# previous as None (already None)
new_node.next = self.head
# 4. change prev of head node to new_node
if self.head is not None:
self.head.prev = new_node
# 5. move the head to point to the new node
self.head = new_node
# Given a node as prev_node, insert a new node after
# the given node
def insertAfter(self, prev_node, new_data):
# 1. Check if the given prev_node is None
if prev_node is None:
print("the given previous node cannot be NULL")
return
# 2. allocate new node
# 3. put in the data
new_node = Node(new_data)
# 4. Make net of new node as next of prev node
new_node.next = prev_node.next
# 5. Make prev_node as previous of new_node
prev_node.next = new_node
# 6. Make prev_node ass previous of new_node
new_node.prev = prev_node
# 7. Change previous of new_nodes's next node
if new_node.next:
new_node.next.prev = new_node
# Given a reference to the head of DLL and integer,
# appends a new node at the end
def append(self, new_data):
# 1. Allocates node
# 2. Put in the data
new_node = Node(new_data)
# 3. This new node is going to be the last node,
# so make next of it as None
# (It already is initialized as None)
# 4. If the Linked List is empty, then make the
# new node as head
if self.head is None:
self.head = new_node
return
# 5. Else traverse till the last node
last = self.head
while last.next:
last = last.next
# 6. Change the next of last node
last.next = new_node
# 7. Make last node as previous of new node
new_node.prev = last
return
# This function prints contents of linked list
# starting from the given node
def printList(self, node):
print("\nTraversal in forward direction")
while node:
print(" {}".format(node.data))
last = node
node = node.next
print("\nTraversal in reverse direction")
while last:
print(" {}".format(last.data))
last = last.prev
# Driver program to test above functions
# Start with empty list
llist = DoublyLinkedList()
# Insert 6. So the list becomes 6->None
llist.append(6)
# Insert 7 at the beginning.
# So linked list becomes 7->6->None
llist.push(7)
# Insert 1 at the beginning.
# So linked list becomes 1->7->6->None
llist.push(1)
# Insert 4 at the end.
# So linked list becomes 1->7->6->4->None
llist.append(4)
# Insert 8, after 7.
# So linked list becomes 1->7->8->6->4->None
llist.insertAfter(llist.head.next, 8)
print ("Created DLL is: ")
llist.printList(llist.head)
# This code is contributed by Nikhil Kumar Singh(nickzuck_007)
C#
// A complete working C# program to demonstrate all
using System;
// Class for Doubly Linked List
public class DLL
{
Node head; // head of list
/* Doubly Linked list Node*/
public class Node
{
public int data;
public Node prev;
public Node next;
// Constructor to create a new node
// next and prev is by default initialized as null
public Node(int d)
{
data = d;
}
}
// Adding a node at the front of the list
public void push(int new_data)
{
/* 1. allocate node
* 2. put in the data */
Node new_Node = new Node(new_data);
/* 3. Make next of new node as
head and previous as NULL */
new_Node.next = head;
new_Node.prev = null;
/* 4. change prev of head node to new node */
if (head != null)
head.prev = new_Node;
/* 5. move the head to point to the new node */
head = new_Node;
}
/* Given a node as prev_node, insert
a new node after the given node */
public void InsertAfter(Node prev_Node, int new_data)
{
/*1. check if the given prev_node is NULL */
if (prev_Node == null)
{
Console.WriteLine("The given previous node cannot be NULL ");
return;
}
/* 2. allocate node
* 3. put in the data */
Node new_node = new Node(new_data);
/* 4. Make next of new node as next of prev_node */
new_node.next = prev_Node.next;
/* 5. Make the next of prev_node as new_node */
prev_Node.next = new_node;
/* 6. Make prev_node as previous of new_node */
new_node.prev = prev_Node;
/* 7. Change previous of new_node's next node */
if (new_node.next != null)
new_node.next.prev = new_node;
}
// Add a node at the end of the list
void append(int new_data)
{
/* 1. allocate node
* 2. put in the data */
Node new_node = new Node(new_data);
Node last = head; /* used in step 5*/
/* 3. This new node is going
to be the last node, so
* make next of it as NULL*/
new_node.next = null;
/* 4. If the Linked List is empty,
then make the new * node as head */
if (head == null)
{
new_node.prev = null;
head = new_node;
return;
}
/* 5. Else traverse till the last node */
while (last.next != null)
last = last.next;
/* 6. Change the next of last node */
last.next = new_node;
/* 7. Make last node as previous of new node */
new_node.prev = last;
}
// This function prints contents of
// linked list starting from the given node
public void printlist(Node node)
{
Node last = null;
Console.WriteLine("Traversal in forward Direction");
while (node != null) {
Console.Write(node.data + " ");
last = node;
node = node.next;
}
Console.WriteLine();
Console.WriteLine("Traversal in reverse direction");
while (last != null) {
Console.Write(last.data + " ");
last = last.prev;
}
}
/* Driver code*/
public static void Main(String[] args)
{
/* Start with the empty list */
DLL dll = new DLL();
// Insert 6. So linked list becomes 6->NULL
dll.append(6);
// Insert 7 at the beginning.
// So linked list becomes 7->6->NULL
dll.push(7);
// Insert 1 at the beginning.
// So linked list becomes 1->7->6->NULL
dll.push(1);
// Insert 4 at the end. So linked list
// becomes 1->7->6->4->NULL
dll.append(4);
// Insert 8, after 7. So linked list
// becomes 1->7->8->6->4->NULL
dll.InsertAfter(dll.head.next, 8);
Console.WriteLine("Created DLL is: ");
dll.printlist(dll.head);
}
}
// This code is contributed by 29AjayKumar
Javascript
<script>
// A complete working javascript program to demonstrate all
// Class for Doubly Linked List
var head; // head of list
/* Doubly Linked list Node */
class Node {
// Constructor to create a new node
// next and prev is by default initialized as null
constructor(d) {
this.data = d;
this.next = null;
this.prev = null;
}
}
// Adding a node at the front of the list
function push(new_data) {
/*
* 1. allocate node 2. put in the data
*/
var new_Node = new Node(new_data);
/* 3. Make next of new node as head and previous as NULL */
new_Node.next = head;
new_Node.prev = null;
/* 4. change prev of head node to new node */
if (head != null)
head.prev = new_Node;
/* 5. move the head to point to the new node */
head = new_Node;
}
// Add a node before the given node
function InsertBefore(next_node , new_data) {
/* Check if the given nx_node is NULL */
if (next_node == null) {
document.write("The given next node can not be NULL");
return;
}
// Allocate node, put in the data
var new_node = new Node(new_data);
// Making prev of new node as prev of next node
new_node.prev = next_node.prev;
// Making prev of next node as new node
next_node.prev = new_node;
// Making next of new node as next node
new_node.next = next_node;
// Check if new node is added as head
if (new_node.prev != null)
new_node.prev.next = new_node;
else
head = new_node;
}
/*
* Given a node as prev_node, insert a new node after the given node
*/
function InsertAfter(prev_Node , new_data) {
/* 1. check if the given prev_node is NULL */
if (prev_Node == null) {
document.write("The given previous node cannot be NULL ");
return;
}
/*
* 2. allocate node 3. put in the data
*/
var new_node = new Node(new_data);
/* 4. Make next of new node as next of prev_node */
new_node.next = prev_Node.next;
/* 5. Make the next of prev_node as new_node */
prev_Node.next = new_node;
/* 6. Make prev_node as previous of new_node */
new_node.prev = prev_Node;
/* 7. Change previous of new_node's next node */
if (new_node.next != null)
new_node.next.prev = new_node;
}
// Add a node at the end of the list
function append(new_data) {
/*
* 1. allocate node 2. put in the data
*/
var new_node = new Node(new_data);
var last = head; /* used in step 5 */
/*
* 3. This new node is going to be the last node, so make next of it as NULL
*/
new_node.next = null;
/*
* 4. If the Linked List is empty, then make the new node as head
*/
if (head == null) {
new_node.prev = null;
head = new_node;
return;
}
/* 5. Else traverse till the last node */
while (last.next != null)
last = last.next;
/* 6. Change the next of last node */
last.next = new_node;
/* 7. Make last node as previous of new node */
new_node.prev = last;
}
// This function prints contents of
// linked list starting from the given node
function printlist(node) {
var last = null;
document.write("<br/>Traversal in forward Direction<br/>");
while (node != null) {
document.write(node.data + " ");
last = node;
node = node.next;
}
document.write();
document.write("<br/>Traversal in reverse direction<br/>");
while (last != null) {
document.write(last.data + " ");
last = last.prev;
}
}
/* Driver program to test above functions */
/* Start with the empty list */
// Insert 6. So linked list becomes 6->NULL
append(6);
// Insert 7 at the beginning. So
// linked list becomes 7->6->NULL
push(7);
// Insert 1 at the beginning. So
// linked list becomes 1->7->6->NULL
push(1);
// Insert 4 at the end. So linked
// list becomes 1->7->6->4->NULL
append(4);
// Insert 8, after 7. So linked
// list becomes 1->7->8->6->4->NULL
InsertAfter(head.next, 8);
// Insert 5, before 8.So linked
// list becomes 1->7->5->8->6->4
InsertBefore(head.next.next, 5);
document.write("Created DLL is:<br/> ");
printlist(head);
// This code is contributed by Rajput-Ji
</script>
Producción
Created DLL is: Traversal in forward direction 1 7 8 6 4 Traversal in reverse direction 4 6 8 7 1
Método alternativo usando la llamada al constructor
Sin embargo, hay otro método que utiliza la llamada al constructor dentro de la clase de Node para minimizar el trabajo de asignación de memoria. También minimiza el número de líneas de código.
C++
// Divyansh Mishra --> divyanshmishra101010
#include <iostream>
using namespace std;
class node{
public:
node* prev;
int data;
node* next;
node(int value){ // A constructor is called here
prev=NULL; // By default previous pointer is pointed to NULL
data=value; // value is assigned to the data
next=NULL; // By default next pointer is pointed to NULL
}
};
void insert_at_head(node* &head, int value){
node* n = new node(value);
n->next=head;
if(head!=NULL){
head->prev=n;
}
head=n;
}
void insert_at_tail(node* &head, int value){
if(head==NULL){
insert_at_head(head, value);
return;
}
node* n = new node(value);
node* temp=head;
while(temp->next!=NULL){
temp=temp->next;
}
temp->next=n;
n->prev=temp;
}
void display(node* head){
node* temp=head;
while(temp!=NULL){
cout<<temp->data<<" --> ";
temp=temp->next;
}
cout<<"NULL"<<endl;
}
int main()
{
node* head=NULL; // declaring an empty doubly linked list
insert_at_tail(head,1);
insert_at_tail(head,2);
insert_at_tail(head,3);
insert_at_tail(head,4);
insert_at_tail(head,5);
cout<<"After insertion at tail: ";
display(head);
cout<<"After insertion at head: ";
insert_at_head(head,0);
display(head);
return 0;
}
Producción
After insertion at tail: 1 --> 2 --> 3 --> 4 --> 5 --> NULL After insertion at head: 0 --> 1 --> 2 --> 3 --> 4 --> 5 --> NULL
Consulte también: Eliminar un Node en la lista de enlaces dobles
Escriba comentarios si encuentra algo incorrecto o si desea compartir más información sobre el tema tratado anteriormente.
Publicación traducida automáticamente
Artículo escrito por GeeksforGeeks-1 y traducido por Barcelona Geeks. The original can be accessed here. Licence: CCBY-SA